Real-world nudging, pricing, and mobile physical activity coaching was insufficient to improve lifestyle behaviours and cardiometabolic health: the Supreme Nudge parallel cluster-randomised controlled supermarket trial

Background Context-specific interventions may contribute to sustained behaviour change and improved health outcomes. We evaluated the real-world effects of supermarket nudging and pricing strategies and mobile physical activity coaching on diet quality, food-purchasing behaviour, walking behaviour, and cardiometabolic risk markers. Methods This parallel cluster-randomised controlled trial included supermarkets in socially disadvantaged neighbourhoods across the Netherlands with regular shoppers aged 30–80 years. Supermarkets were randomised to receive co-created nudging and pricing strategies promoting healthier purchasing (N = 6) or not (N = 6). Nudges targeted 9% of supermarket products and pricing strategies 3%. Subsequently, participants were individually randomised to a control (step counter app) or intervention arm (step counter and mobile coaching app) to promote walking. The primary outcome was the average change in diet quality (low (0) to high (150)) over all follow-up time points measured with a validated 40-item food frequency questionnaire at baseline and 3, 6, and 12 months. Secondary outcomes included healthier food purchasing (loyalty card-derived), daily step count (step counter app), cardiometabolic risk markers (lipid profile and HbA1c via finger prick, and waist circumference via measuring tape), and supermarket customer satisfaction (questionnaire-based: very unsatisfied (1) to very satisfied (7)), evaluated using linear mixed-models. Healthy supermarket sales (an exploratory outcome) were analysed via controlled interrupted time series analyses. Results Of 361 participants (162 intervention, 199 control), 73% were female, the average age was 58 (SD 11) years, and 42% were highly educated. Compared to the control arm, the intervention arm showed no statistically significant average changes over time in diet quality (β ﻿− 1.1 (95% CI ﻿− 3.8 to 1.7)), percentage healthy purchasing (β 0.7 ( ﻿− 2.7 to 4.0)), step count (β ﻿− 124.0 (﻿− 723.1 to 475.1), or any of the cardiometabolic risk markers. Participants in the intervention arm scored 0.3 points (0.1 to 0.5) higher on customer satisfaction on average over time. Supermarket-level sales were unaffected (β − 0.0 (− 0.0 to 0.0)). Conclusions Co-created nudging and pricing strategies that predominantly targeted healthy products via nudges were unable to increase healthier food purchases and intake nor improve cardiometabolic health. The mobile coaching intervention did not affect step count. Governmental policy measures are needed to ensure more impactful supermarket modifications that promote healthier purchases. Trial registration Dutch Trial Register ID NL7064, 30 May 2018, https://www.onderzoekmetmensen.nl/en/trial/20990 Supplementary Information The online version contains supplementary material available at 10.1186/s12916-024-03268-4.

Real-world nudging, pricing and mobile physical activity coaching was insufficient to improve lifestyle behaviours and cardiometabolic health: the Supreme Nudge parallel cluster-randomised controlled supermarket trial

Supplementary figures
Josine M Stuber, et al

Figure S4 .
Figure S4.Average total cholesterol to HDL ratio over time for different age levels in the intervention group (nudging and pricing strategies) and the control group of the Supreme Nudge trial (n=290).Analysis was based on a linear mixed model including all follow-up time points and with random intercepts for supermarket location and for participant, including the total cholesterol to HDL ratio baseline value as covariate............

Figure S3 .
Figure S3.Average waist circumference among females over time for different age levels in the intervention group (nudging and pricing strategies) and the control group of the Supreme Nudge trial (n=239).Analysis was based on a linear mixed model including all follow-up time points and with random intercepts for supermarket location and for participant, including the waist circumference baseline value as covariate.

Figure S4 .
Figure S4.Average total cholesterol to HDL ratio over time for different age levels in the intervention group (nudging and pricing strategies) and the control group of the Supreme Nudge trial (n=290).Analysis was based on a linear mixed model including all follow-up time points and with random intercepts for supermarket location and for participant, including the total cholesterol to HDL ratio baseline value as covariate.

Figure S5 .
Figure S5.Mean implementation fidelity scores (range 1-5) per month over the intervention period of one year, by supermarket.